"For this difficulty, which I have purposely stated in the strongest terms it would admit of, the school of metaphysicians, who have long predominated in this country, find a ready salvo. They affirm that the universality of causation is a truth which we cannot help believing; that the belief in it is an instinct, one of the laws of our believing faculty. As the proof of this they say, and they have nothing else to say, that every body _does_ believe it; and they number it among the propositions, rather numerous in their catalogue, which may be logically argued against, and perhaps cannot be logically proved, but which are of higher authority than logic, and which even he who denies in speculation, shows by his habitual practice that his arguments make no impression on himself. "I have no intention of entering into the merits of this question, as a problem of transcendental metaphysics. But I must renew my protest against adducing, as evidence of the truth of a fact in external nature, any necessity which the human mind may be conceived to be under of believing it. It is the business of human intellect to adapt itself to the realities of things, and not to measure those realities by its own capacities of comprehension. The same quality which fits mankind for the offices and purposes of their own little life, the tendency of their belief to follow their experience, incapacitates them for judging of what lies beyond. Not only what man can know, but what he can conceive, depends upon what he has experienced. Whatever forms a part of all his experience, forms a part also of all his conceptions, and appears to him universal and necessary, though really, for aught he knows, having no existence beyond certain narrow limits. The habit, however, of philosophical analysis, of which it is the surest effect to enable the mind to command, instead of being commanded by, the laws of the merely passive part of its own nature, and which, by showing to us that things are not necessarily connected in fact because their ideas are connected in our minds, is able to loosen innumerable associations which reign despotically over the undisciplined mind; this habit is not without power even over those associations which the philosophical school, of which I have been speaking, regard as connate and instinctive. I am convinced that any one accustomed to abstraction and analysis, who will fairly exert his faculties for the purpose, will, when his imagination has once learned to entertain the notion, find no difficulty in conceiving that in some one, for instance, of the many firmaments into which sidereal astronomy now divides the universe, events may succeed one another at random, without any fixed law; nor can any thing in our